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NATURALIZATION OF AMERICAN FISHES IN AUSTRIAN 

WATERS 

J* 

By Franz von Pirko 

President of the loipcyial and Royal Ansln'aii Fishery Soeiefy 

Paper presented before the Fourth International Fishery Congress 
held at Washington, U. S. A., September 22 to 26, 1908 

BULLETIN OF THE BUREAU OF FISHERIES :::::: VOL. XXVIll. P. 977-982 
Document No. 698 ::::::::::::::::::::: Issued April, 1910 



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■'' 1910 



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NATURALIZATION OF AMERICAN FISHES IN AUSTRIAN WATERS. 



By FRANZ VON PIRKO, 
President uj llw Imperial and Royal Auslrian Fishery Society. 



In the belief that it might greatly interest American fish breeders to know 
what experiences and observations have been made by Austrian pisciculturists 
in regard to fish imported from America for breeding purposes, and in compliance 
with a special invitation from the committee of the Fourth International Fishery 
Congress, Washington, 1908, the Imperial and Royal Austrian Fishery Society 
has called upon the prominent fish breeders to funiish their observations regard- 
ing the results obtained with such American fish. These results, which are 
briefly set forth here, warrant the conclusion that of all the Salmonidie which 
can be taken into account for breeding purposes the American rainbow trout 
must be regarded as the most important. This trout, which has now been in 
Austrian waters for a quarter of a century, despite manifold opposition has 
gained, so to say, the rights of citizenship there. Owing to its excellent qualities 
it has been tiuickly introduced into all pond fisheries and is really a first-class 
salmonid. In consequence of its ability to endure deep water, the numljer of 
ponds in which it can grow is quite considerable, and pond-fish owners would be 
well advised to allow plenty of room for the rainbow trout, without forgetting, 
however, that after all it is a salmonid. Its capacity to stand high temperatures 
enables it to replace the pike in carp ponds, the more so as it does not possess 
the dangerous qualities of the latter. 

The irideus is just as indifferent to high temperatures as to cold. Therefore 
at a time when theSa/w/o fonlhialis, or brook char, and the native l^rook trout have 
long ceased to take food the irideus still comes to its meals, and the advantage 
offered to the breeder by its appetite, displayed even when the pond is covered with 
ice, must not be underestimated. In addition to this its power of resistance 
against diseases is amazing. It is not only — perhaps owing to its perceptibly 
thicker skin — far less exposed to the attacks of the malignant Saprolegniaceae 
than all the other vSalmonida;, and therefore very rarely seized with fungus, but 
it also appears to possess immunity from the most dangerous bacterial diseases, 
such as furunculosis. Its indifference to polluted waters enables it to live in water 

979 



980 BULLETIN OF THE BUREAU OF FISHERIES. 

courses where no other sahnonid could thrive. Even in the immediate neighbor- 
hood of factories discharging waste water and refuse, where both the brook trout 
and the char could certainly not exist, the iridens flourishes and grows fat. 
It appears to be specially valuable for exclusively or partiall)' populating the 
numerous cold ponds in the forests of lower Austria, which in consequence of 
their low temperature, severe climate, and exposed situation are less adapted 
for carp breeding. Altogether it must be said that the iridcus has fully come up 
to all that has been expected from it in nearly every instance. 

Thus until very recentlN' all breeders joined in a panegyric of the irideus. 
But things have now changed. The sad discovery has been made that the 
much-praised power of resistance of the rainbow trout in ponds against disease 
rapidly decreases and that this fish if strongly fed nowadays suddenly shows a 
remarkable frailty, nay an exotic weakness, which had been entirelj' unforeseen. 
The most unpleasant phenomenon for the breeder is the increasing spread of 
anaemia, which frequently causes great losses. The extraordinary weakness 
becomes manifest in the death of numerous lisli through simple sorting opera- 
tions, the clearing out of ponds, or short transportation. Quite frequently 
examination of the dead fish reveals no other symptoms but those of a greater 
or less poorness of blood. The fish are pale, particularly in the gills, the regular 
color of which ought to be a very bright red. The internal organs are also pale, 
and the liver yellow. This organ frequently shows fatty degeneration and is 
interspersed with hemorrhages, as the result of ruptures of the sides of the 
vessels. Searches for any other causes, such as bacteria and parasites, have 
proved unsuccessful. Consequently anaemia must be regarded as a symptom 
of general deterioration of the breed. As a rule these symptoms become visible 
in the second year, and it may be that frequently the death of the fry as well 
as the outbreak of dropsy of the yolk sacs is due to this circumstance. As a 
matter of course such fish are not very well qualified to act later as mother fish, 
as they give bad eggs and sometimes remain sterile because of degeneration of 
the sexual organs. Undoubtedly the unfitness of the rainbow trout for 
acclimatization here is the cause of this degeneration. The conditions in which 
the fish lives in its native country, where it migrates even at the spawning 
time, are it appears different from those in Austria. It may therefore be truly 
said that the rainbow trout is decreasing at a rapid rate and before long will 
disappear from our ponds, unless there is a speedy introduction of fresh blood 
by the importation of eggs from America. In the unfortunately somewhat 
limited numlier of brooks and small rivers which for some time have been 
stocked with iridcus in a regular and rational manner, a good stock has developed 
which spavn in open water and multiply in a natural way although not in great 
numbers. These do not show any of the symptoms of degeneration of the pond 
and fattened fish of this species. 



AMERICAN FISHES IN AUSTRIA. 981 

Not less valued than the rainbow trout was the American brook char, Sal- 
velinus fontinalis. It is true it was less utilized than the irideus, as it can only- 
live in spring water; its breeding gave very satisfactory results, however, in the 
first years after its introduction. Not inferior to the irideus as regards early 
growth, it behaved excellently even in ponds watered exclusively by precipitation 
of the atmosphere and it appeared as though the brook char might be qualified to 
replace our brook trout, whose breeding offers far greater difficulties. In the 
course of time, however, these sanguine expectations gave place to bitter disap- 
pointment, and it became obvious that all the hopes entertained were chimerical. 

Even before birth the char causes great trouble. The losses in eggs are enor- 
mous, as despite scrupulous attention at spawning time the number of sterile 
eggs is great beyond measure, and miscarriages are far more frecjuent than with 
other fish. On the other hand, it is true that the bringing-up of the brood gives 
very little trouble. The small fish take artificial food very early and in autumn 
the pond is alive with fry. But soon an unpleasant feature becomes visible, viz, 
premature growth, which attribute is the more unfortunate as the char indulges 
in cannibalism more than any other fish. In this respect it comes very near the 
pike. Its voracity very greatly promotes its growth in the first and second 
years, but later it suddenly stops growing and fine large fish are seldom seen. 

Its capacity to resist disease, which quality we value so highly in the 
irideus, is extremely small. Bacterial infections, fungus, and intestinal disorders 
often kill whole stocks, and it is also much more liable to furunculosis than is its 
American brother. Besides, the char suffers from a peculiarly special form of 
petechial affection. This manifests itself in irregularly shaped flat defects of the 
surface skin, dull gray spots with byssus, the origin of which has not yet been 
definitely ascertained. This disease has discouraged many pisciculturists from 
continuing to breed the foutiiialis. 

Another circumstance must be mentioned which makes the cultivation of 
the brook char in the second year very unprofitable, namely, degeneration of the 
eggs caused by overfeeding. That the brood product of such fish as are 
artificially fed is entirely- worthless would be a lesser evil were it not also that 
the fish themselves perish in great numbers at the spawning time through over- 
fattening of the internal organs. It is chiefly the spawners that die, as they can 
not deposit their spawn, which is not thoroughly and normally matured. The 
char, moreover, requires special qualities and temperature of water. It only 
thrives in hard, clear spring water of even temperature ranging from 42° to 54^ F. 
The risk connected with its fattening rapidly increases with rising temperature 
of water, whilst if this is much below the above-mentioned degrees the food taken 
no longer affords proper nourishment. It has often been proposed to rear the 
char in running water, but to this the objection must be made that the char 
would immediately become too formidable a competitor of our brook trout with 



982 BULLETIN OF THE BUREAU OF FISHERIES. 

regard to feeding, and in all likelihood there is hardly a pisciculturist who would 
be prepared to substitute the brook char, which can not be disposed of so easily 
here, for the popular brook trout. For these reasons the breeding of the brook 
char has been generally neglected in Austria for the last few years, and in some 
fisheries has even been abandoned altogether. 

A promising future appears to lie before the pur pur at a. In growth it 
develops as rapidly as the irideus and it thrives under the same conditions. 
Its brilliant exterior and slender body, similar to that of the brook trout, are 
advantages which must not be underestimated. So far, however, the purpurata 
is bred in Austria only in isolated fisheries, and it would be premature to-day to 
pronounce a definitive decision regarding the value of this beautiful fish to 
breeders. 

The American black bass, Micropterus sahnoides, is being bred in several 
pond fisheries side by side with carp. The conditions of growth are favorable. 
The objections raised against this fish are that it is a great truant and extremely 
sensitive to the effects of muddy water, which latter occasions great losses in the 
clearing out of ponds. There is also no great demand for the fish, though it is 
fleshy and palatable, for the public show a certain aversion to the disproportion- 
ate size of the head, which, in fact, equals a quarter of the weight of the whole 
fish. As the fish is tenacious of life, however, can be easily transported, and is 
not very dainty in feeding, it may be that in time it will become more popular, 
especially if breeders succeed in producing it with a smaller head. In the 
tributaries of the Danube and in pools and stagnant water it could not exist at all. 

The tiny California sheatfish is not yet well known in Austria, and as its 
many good qualities are much underestimated it is not very popular. It is a 
harmless fish, extremely tenacious of life, and, like the black bass, is often bred 
in carp ponds. As it is a decided mud fish, attempts have been made to introduce 
it in waters in which our finer fish have been destroyed through the discharge 
of factory refuse, river regulating works, and exploitation of water power. The 
tiny sheatfish has fulfilled all the hopes placed in it and thrives splendidly even 
in strongly polluted waters. Though it offers only an inferior substitute for our 
better kinds of fish, it may yet perhaps be destined to play an important part in 
Austrian pisciculture. 

From all this it follows that our most precious acquisition from America is 
the rainbow trout, as we do not yet sufficiently know the purpurata, provided 
that we shall be able to renew the breed by the speedy importation of eggs from 
America, and in this conviction we heartily join the Austrian pisciculturist who 
writes at the close of his observations, "May our friends in America add a new 
gift to that which they have made us already in the irideus, and give us a little 
from their superabundance. The fish breeders of Austria would be very grateful 
to them." 



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Hollinger Corp. 

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